The invention relates to an apparatus for continuously adjusting the length of a lifting sling designed to carry a load. Such lifting slings generally comprise flat woven textile slinging means which can be equipped with loops for attaching to the hook of a transport crane.
Lifting slings with loops or in continuous form (belt slings) are known from the old DIN 61360 or the new DIN EN 1492-1. In each case, they serve as slinging means with a precisely defined working length. By equipping these lifting slings with suitable fittings such as D-clamps, they form suspension attachments which can be suspended from a crane hook. Additional forged coupling elements and hooks also can form part of the known suspension attachments.
The known lifting slings are only available in each case in a fixed length predefined by the manufacturer or user. In practice, the length of the lifting slings can only be suitably adapted to the particular transport problem to be overcome by using a high-strength slinging chain whose length can be adjusted using chain shorteners. This makes the handling of known lifting slings complicated and limits the field of application.
The object of the invention is to improve the versatility of lifting slings of the type mentioned above.
This object is achieved by an apparatus for continuously adjusting the length of a lifting sling designed to carry a load, which comprises a U-shaped clamp having a central region and legs projecting from the central region, each of the legs having a bearing for supporting a swivel axis member, a load-lifting element secured to the clamp to which the load can be attached, and a clamping element supported on the swivel axis, the load-lifting element having:(i) two side legs running parallel to one another and separated from each other by a distance, each side leg having one free end coupled to the swivel axis member, (ii) an end cross-piece formed at the other end of at least one of the side legs which spans the distance between the side legs, and (iii) a center cross-piece arranged between the end cross-piece and the swivel axis member. The swivel axis member, the central part of the U-shaped clamp, the center cross-piece, and the end cross-piece are preferably substantially axially parallel one to another.
An apparatus constructed according to the invention is intended to be attached to the unlooped end of a lifting sling. For this purpose, the apparatus on the one hand has a U-shaped clamp to which the load to be carried is attached. On the other hand, the apparatus according to the invention is provided with a clamping element via which the coupling with the lifting sling is made. This clamping element is designed so that the coupling between the lifting sling and the apparatus is made in a simple fashion and the required length of the lifting sling can be varied just as simply.
Thus, in the load-free state the apparatus according to the invention swivels into a threading-in position in which the lifting sling can be suitably positioned about the cross-pieces of the clamping element and the swivel axis without the action of forces impeding the threading process. Then the apparatus is swivelled into its load-lifting position in which movement of the belt length is prevented by self-locking in the apparatus. At the same time, since the U-shaped clamp coupled to the load is flexibly coupled via a swivel axis to the clamping element forming the coupling to the lifting sling, this ensures that the forces to be absorbed during transport of the load are always introduced into the lifting sling in an optimal fashion. By bringing the apparatus into a position located between the threading-in position and the load-lifting position, this self-locking can be loosened to an extent such that the length of the lifting tool can be adapted to the particular requirements without any problem.
The apparatus according to the invention is thus a connecting element which makes it possible to couple loads of various types and shapes to a single lifting sling in the sense of a modular system. The invention not only allows the length of the lifting sling to be varied arbitrarily, but also allows attachment to the U-shaped clamp of a wide range of connecting elements and hooks which are best suited to the particular transport problem to be overcome.
The advantages of using an apparatus according to the invention especially emerge when intricately shaped loads are to be transported on multi-strand suspension attachments. By coupling each individual strand of such a suspension attachment to the load via an apparatus according to the invention, the length of each strand can be adapted to the required geometry and the center of gravity of the load without any problem, so that the safest possible transport can be ensured even for loads having a non-uniform geometry.
The forming of the U-shaped clamp can be simplified by constructing the elements required to attach the load-lifting element at the central part of the U-shaped clamp. However, it is just as feasible to form suitable elements at the legs of the relevant clamp. With reference to an optimum introduction of the forces to be absorbed into the clamp and the lifting sling coupled to the clamp during transport, it is favorable if the load-lifting element is flexibly supported on the U-shaped clamp.
An embodiment of the apparatus according to the invention which substantially facilitates threading in the lifting sling is characterised by the fact that the first side leg carrying the end cross-piece is longer than the second side leg of the clamping element. In this way, between the end of the end cross-piece and the free end of the second side leg there is a free space through which the lifting sling can be pushed. With reference to the safety of the self-locking under load, it is favorable if the free end of the end cross-piece is arranged facing the end of the second side leg assigned to it and at some distance from this end. This ensures that the lifting sling is supported on the end cross-piece over its entire width. The safety of guiding the belt in the clamping element is further improved by the end cross-piece having at its free end an extension oriented towards the end of the second leg. This extension reliably prevents the belt from sliding out of the clamping element in the load-free state or during adjustment of the length. The same purpose is served if the second side leg has its end assigned to the end cross-piece projecting above the position at which it is connected to the center cross-piece. The section projecting above the end cross-piece prevents the belt from slipping from the centre cross-piece.
The components of an apparatus according to the invention can be manufactured particularly economically by forging.